The idea that certain calendar dates are lucky or unlucky is of ancient origin, going back as far as the
Mesopotamian civilizations. Tables that identify lucky and unlucky days are sometimes known by their German category name
Tagwählerei. • The
Coligny calendar identifies certain calendar dates as lucky (
mat) or unlucky (
anmat). • The
Roman calendar marks many days and parts of others as
dies nefasti, religiously unsuitable for the conduct of public business. • Contemporary North America has a tradition that
Friday the 13th is an unlucky day. It has been called a "pervasive form of divination" that "is found in all societies which regulate their days and nights in calendric system". The received idea concerning the origin of Tycho Brahe days was that : "Tycho Brahe, the celebrated Danish astronomer of the sixteenth and seventeenth centuries, was very superstitious, considering certain days in the year pregnant with misfortune, wherefore in Denmark, up to this very day, the laboring class call such days on which they happen to meet with some unfortunate accident, ''Tycho Brahe's days''." In his travelogue ''A Poet's Bazaar'',
Hans Christian Andersen alludes to Tycho Brahe's death while living in exile, in Prague, observing that : "Denmark owns not even his dust; but the Danes mention his name in their bad times, as if a denunciation proceeded out of it: These are 'Tycho Brahe's days!' they say." They are still frequently referenced in
almanacs and recur in Scandinavian folklore. In the
Cyprianus tradition, Tycho Brahe days are considered unlucky for magical work; several of the spells in the
Black Books of Elverum note that they should not be carried out on a Tycho Brahe day. ==Days==